ACTION OF CYTOST 121 



An alternative explanation may, however, be of- 

 fered, for at this temperature some of the water- 

 soluble proteins in the extract are coagulated, and it is 

 conceivable that the active constituent of the embryo 

 juice may be absorbed upon the coagulum and thus 

 become unavailable to the growing tissue. This con- 

 cept is in harmony with Carrel's (1913) observation 

 that the growth-promoting stimulant is removed from 

 the embryo extracts when the latter are passed through 

 a Chamberland filter, which presumably absorbs the 

 active substance. 



The conclusion to be drawn from these investiga- 

 tions is simply that cells in tissue culture require, aside 

 from adequate food, some substance which stimulates 

 in some fashion their metabolism and growth. We 

 shall now pass to some related experiments conducted 

 by the author (Turck, 1921). 



The reader may recall the author's experiments, in 

 which mustard infusions were introduced into the 

 stomachs of dogs, and that such treatment, if pro- 

 longed, results, as stated previously, in severe inflam- 

 mation of the gastric mucosa and eventual destruction 

 of the mucous membrane and gland cells, although the 

 surface epithelium is not so seriously damaged as are 

 the deeper tissues. This fact, it may be remembered, 

 led to the conclusion that the latter were affected, not 

 by the mustard, but by substances released from the 

 surface epithelium under the destructive action of the 

 mustard. Further histological examination disclosed 

 distinct evidence of mitosis in the affected tissues; 

 hence we are led to conclude that cytost, aside from 

 its toxic action, may actually be a stimulant of cellular 

 metabolism and growth. 



